[tpm2] Re: Re-provision TPM

[Anthony Arrascue <AArrascue at neuroloop.de>]

[-- Attachment #1: Type: text/plain, Size: 4327 bytes --]

Hi Luke,

Thank you. You are right. I should start reading the changelog more often. I have already faced problems in the past with different versions of the tools.
You made me noticed it would have been useful to mention the versions of the tools I was using in my example:

TPM2-TSS v. 2.4.x
TPM2-TOOLS v. 4.X

Best,
Anthony


From: @rubynerd <x(a)rubynerd.net>
Sent: Wednesday, 30 June 2021 12:18
To: Anthony Arrascue <AArrascue(a)neuroloop.de>
Cc: tpm2(a)lists.01.org
Subject: Re: [tpm2] Re: Re-provision TPM

Hi Anthony,

I'm also new to the tpm2-tools project, and whilst I cannot advise on most of the asks in your email, I can confirm the tpm2_takeownership command was changed to tpm2_changeauth, which offers similar functionality.

Further information is available in the changelog: https://github.com/tpm2-software/tpm2-tools/blame/master/doc/CHANGELOG.md#L867-L872

There's quite a bit of movement between what's currently in source control and the snippets floating around on StackOverflow, the changelog is a really good resource for reconciling these. One thing to note: if you're building this from source, the commands have changed from "tpm2_commandname" to "tpm2 commandname", which was another pitfall I fell into during my explorations.

Regarding the specifics of EKs and the differences/functionality of the APIs themselves, I'm afraid I'm woefully out of my depth!

Hope this helps,
Luke

On Wed, Jun 30, 2021 at 11:07 AM Anthony Arrascue <AArrascue(a)neuroloop.de<mailto:AArrascue(a)neuroloop.de>> wrote:
A way of re-provisioning (on a different OS image) that worked for me is the following:

tpm2_startup
#This clears the persistent storage
tpm2_clear
#To change profile from ECC to RSA
sed -i 's/"profile_name": "P_ECCP256SHA256"/"profile_name": "P_RSA2048SHA256"/g' /usr/local/etc/tpm2-tss/fapi-config.json
#Delete existing keystores
rm -rf ~/.local/share/tpm2-tss/user/keystore
rm -rf /usr/local/var/lib/tpm2-tss/system/keystore
#Before we provision we need to generate an EK
tpm2_createprimary -C e -g sha256 -G rsa -c endorsementprimary.ctx
tpm2_create -C endorsementprimary.ctx -g sha256 -G rsa -u rsak.pub -r rsak.priv
tpm2_load -C endorsementprimary.ctx -u rsak.pub -r rsak.priv -n rsak.name<http://rsak.name> -c rsak.ctx
tpm2_evictcontrol -c rsak.ctx 0x81010001
tss2_provision

Without the tpm2_createprimary I would get an error when I use tss2_provision (something like “key cannot be signed”. I cannot remember the error message, but it contained the word EK).

Some questions that came to my mind:

  1.  Can all of this be done using only Fapi (no tpm2 commands)
  2.  Why is generating an EK required for provisioning? (which documentation describes this step)
  3.  Previous versions of the tpm2-tools had also a tpm2_takeownership. What happened with it and how to provision with owner’s authorization?

Thank you very much for your comments.
Best,
Anthony





From: Anthony Arrascue
Sent: Tuesday, 1 June 2021 19:18
To: 'tpm2(a)lists.01.org<mailto:tpm2(a)lists.01.org>' <tpm2(a)lists.01.org<mailto:tpm2(a)lists.01.org>>
Subject: Re-provision TPM

Hello,

I am learning about the TSS and TPM techonologies.
I have provisioned the TPM with the default settings, which means I am now using the ECC profile (P_ECCP256SHA256).
However, encryption was a requirement I needed to fulfill. I just didn't know that ECC encryption is currently not supported and now I realize RSA would be a better fit for me.
So here is my question:

  *   I see there is another profile in /usr/local/etc/tpm2-tss/fapi-profiles, namely P_RSA2048SHA256.json. Is there a way I can encrypt using the RSA profile instead of the ECC one? I tried to re-run tss2_provision, after setting it in fapi-config.json, but it seems this is not the way to proceed. I get the message that the TPM has been already provisioned. What is the correct way of "changing" profile? Is it even possible or do I need to reset the TPM?
Thank you for your help.
Anthony Arrascue

_______________________________________________
tpm2 mailing list -- tpm2(a)lists.01.org<mailto:tpm2(a)lists.01.org>
To unsubscribe send an email to tpm2-leave(a)lists.01.org<mailto:tpm2-leave(a)lists.01.org>
%(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s

[-- Attachment #2: attachment.htm --]
[-- Type: text/html, Size: 22211 bytes --]